Here is the full list of all 119 Torchlight II achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Destroy 10 socketed gems
Have 100,000 gold
Explode 10,000 enemies
Use 10 maps
Use a map
Have 50 friends
Have 10 friends
Defeat the Nether King in Casual difficulty
Defeat the Nether King in Normal difficulty
Defeat the Nether King in Veteran difficulty
Defeat the Nether King as an Embermage
Defeat the Nether King
Join a multiplayer game
Add a friend
Die with a hardcore character
Start a hardcore character
Defeat the Dark Alchemist
Defeat 500 champions
Defeat Vyrax
Take 100,000 steps
Defeat Thiss
Defeat Cacklespit
Do 10,000 damage with a single attack
Obtain a tier 2 skill bonus
Defeat the Wraith Lord
Break 1,000 breakables
Defeat Bloatfang
Defeat the Grizzled Alpha
Defeat Boletus Rex
Deal 10,000 critical strikes
Fish 100 times
Open 500 chests
Defeat the Siege Guardian
Defeat Ezrek Khan
Defeat Aruk
Use an enchanter 50 times
Defeat the King In Masks
Take 50,000 steps
Use 500 potions
Socket 50 gems into items
Defeat the Artificer
Defeat the Manticore's Mate
Defeat the Manticore
Teach a pet 4 spells
Teach a pet a spell
Find a legendary item
Defeat Killbot
Defeat Grand Regent Eldrayn
Fish using dynamite
Defeat Kidrik the Mauler
Defeat Chillhoof
Sell 500 items
Defeat 100 champions
Defeat King Pogg
Recover 10 gems from items
Deal 1,000 critical strikes
Use an enchanter 10 times
Destroy a socketed gem
Obtain a tier 1 skill bonus
Defeat the Winter Widow
Explode 1,000 enemies
Recover a gem from an item
Defeat General Grell
Find a secret room
Learn 4 spells
Wear a completed armor set
Defeat Mordrox
Take 10,000 steps
Learn a spell
Defeat One-Eyed Willy
Use 50 potions
Defeat 25 champions
Open 100 chests
Fish 10 times
Socket a gem into an item
Trade an item with another player
Start a multiplayer game
Defeat the Fallen Guardian
Send your pet to town
Break 100 breakables
Explode 100 enemies
Open 20 chests
Defeat the Nether King with each of the 4 classes
Defeat the Nether King as a Berserker
Defeat the Nether King in Elite difficulty
Defeat the Nether King as an Engineer
Defeat the Nether King in hardcore mode (casual)
Defeat the Nether King in hardcore mode (elite)
Defeat the Nether King in hardcore mode (normal)
Defeat the Nether King in hardcore mode (veteran)
Defeat the Nether King as an Outlander
Break 10,000 breakables
Deal 100,000 critical strikes
Use an enchanter 500 times
Fish 1,000 times
Purchase 20 items from the gambler
Purchase 50 items from the gambler
Purchase 100 items from the gambler
Have 1,000,000 gold
Have 10,000,000 gold
Begin new game plus
Recover 100 gems from items
Destroy 100 socketed gems
Find 10 secret rooms
Find 100 secret rooms
Sell 5,000 items
Sell 50,000 items
Obtain a tier 3 skill bonus
Socket 500 gems into items
Use 100 maps
Use 5,000 potions
Assemble TrillBot
Defeat Aleera
Squish 100 critters
Squish 500 critters
Squish 1000 critters
Defeat Marishka
Defeat Verona
Reach level 100